Lens-testing instrument



. Mai'. 3, 1925.

H. WATSON LENS TESTING INSTRUMENT' 2 sheds-sheet 1 Filed June 18,' '3924 Mar. A3, 1925. T 1-,512s,138 H. WATSON I LENS TESTING INSTRUMENT Filed June 18r 1924 2 sheets-sheet 2 i how much the lens is ofi center.

Patented Mar. 3, 1925.

UNITED STATES PATENT. OFFICE. i

HARRY WATSON, 0F JACKSON, MISSISSIPPI,

LENS-TESTING INSTRUMENT.

Application filed June 18, 1924. Serial No. 720,810.

To all wiz/0m t may concern:

Be it known that I, Dr. Hanniv "WA'rsoN, a

citizen of the United States, residing at Jackson, inthe county of Hinds and State of Mississippi, have invented a new and usey utility of devices of that sort to which the invention appertains. p n

' Although a preferred form has been shown, an instrument-maker workingjwith-l in the scope of what is claimed, may make changes, without departing `from the spirit of the invention;

. In the drawings z-fFigure 1 shows in perspective, a deviceconstructed in accordance with .the invention; Figure v.2 isa section showing a portion of the` upper part of the frame; Figure 3 is a cross section on the line rAB of Figurel, looking inthe direction of the arrows 3 3; Figure 4 is a section on the lineA-B of Figure 1, looking in the Vdirection of the arrows 44; and Figures 5, (3y l 7 and 8 are diagrams illustrating the opera- 3 tion of the instrument. f

The device forming the subject matter. of this applicationcomprises a frame 1 which may be variously constiucted,v the frame, if

desired, comprising a top 2, a base 3, and

standards 4 connectingthe `base 'and the top at the corners thereof. The top 2 carries an eye piece 5 having a tapered passage 6, the least diameter ofthe passage being indicated in Figure 2 by the numeral 7. A. sheet 8 may be mounted on the lower surface of the top 2 and has an opening 9 registerv ing with the wider end of the passage 6 in the eye piece 5. On the sheet 8 is inscribed a protractor 10, thevnumerals of which are reversely placed. The Y protracto-r 10 includes an inner circle 11, radial lines 12 ex tended inwardly to the said circle and radial lines 14 andY 15 extended inwardly to the opening 9 in the sheet 8, the lines 14 and 15l being heavier than the lines 12 and beingdise posed at right angles toA each other'.y At thev outer ends of the radial'lines 12, 14 and 15 the graduations 16 of the protractor are placed. Parallel lines 17. connect the ends of certain of the radial lines 12 and are disposed parallel to the lines 14, at one side thereof;

.y The base 3 of the frame 1 carries a mirror 18. The mirror 18 is provided with a circular mark 19 disposed in the prolonged axis of the passage 6 in the eye piece` the mark 19 preferably being of the same diam- Y eter as the'most constricted portion? of the passage 6 in the eye piece 5, to avoid, so vfar as possible, errors due to parallax. The protractor 10 is reflected in the mirror 18, as shown at 20'in Figure 4, and appears erected in the mirror, when the operator peers downwardly through the passage 6 of the eye piece 5, because the protractor is reversely inscribed on the sheet 8. The mii ror 18 is supplied with a plurality of marks 21 denoting different radial distances from the mark 19, and, more specifically, from the -inner circle 11 of the protractor. The

marks 21 areso spaced that the distance between any two of them represents one diopter, the marks being so disposed that the amount that/they are magnified is negligible, themagni-fication, d'ue to the presence of a lens in theinstrument, being confined to the reflection' of the inner circle-.11 of the on one edge with an index` 22 whichV should be toward the observer is in operation.

Referring to Figure 5, suppose that the when the instrument operator wishes toA test` a spherical Vlens 23 (which happens to be correctly centered), The lens 23 is placed on the mirror 18 and the operator looks downwardly through the' eye piece 5, the lens being shifted about until its geometrical center registers with the mark 19 on the mirror 18. The cross formed by the' lines 14 and 15 remains unbroken, and these lines appear at right angles to each other, itv tliuslbeing made ,manifest that the lens is correctly centered and has noprism. Referringy to Figure 4, it will be observed that thek innermost one Vof the marks 21 is spaced froinlthe inner kcircle 11 of the protractor 10, Lwhen there is Yno lens,4 on' the mirror" 18. Reverting to it ,will be observed that when thel lens 23 is" placed on iosthe niirror 18, the-innermoet vone oit the marks 21 coincidesI with the inner circle 11 of the protractor 10, as i-efiected in the iiiirror 18, and the operator is advised thatthe power of the lens is one diopter.

Passing to Figure 6, a cylindrical lens 24 is shown in place on the inirror 18. The lines 14 and 15 remain unbroken, but the inner circle 11 is distorted into an ellipse, thus'sliowing that tlie lens is a cylinder.

As shown 1in Figure 7, "the lens 24 may be rotated clockwise until the distorted portion 2510i' the line 14 coincides lwith one of the radial lines "12 as reflected lin the mirror, and by noting the appropriategraduations 16,' the angular position of `the axis of Vthe cylinder -inay b e determined. VBy rotating the lens 24 'counter-clockwise, 'until the distorted portion 25 oi' the 'line 14 coincide-s with-the outer end of o-ne of the ylines 17, the cylindric power of the lens in diopters maybe ascertained through a suit- Iable calibration of the lines 17.

In Figure 8", a `cle-centered prisniatic llens 26 is shown in place, and it will be observed that the lens causes a part of the line 14 to be offset as shown at 27, and the-'part- 27 of ythe line 14, cooperating with the appropriate one "of thelines 17 indicates vhow inucli the vlens is oil1 center. IBy sliding the lens 26 until the line 14 appears continuous, that is, until there is no apparent offset like the ,part 27 of the line 14, the operator rmay lascertain the optical center of the lens.

What is claimed is 1. An linstrument for testing lenses, coinprising a top having an eye piece, and a base having-a inirror provided with a center point cooperating' with the eye piece,

vthe top being" provid'eidwith a protractor so ylocated as to be reflected in the mirror about the center point, lthe protractor Vcomprising an inner circle and radial lines extended outwardly from the circle, certain of theradialflines which are vat right angles to each 'other being-accentuated to'form a cross.

2. An instrument for testingdenses, coni- .vprising a top having an eye piece,and a base'having a mirror Yprovided with a cenvbase :having a niirror provided witha center point cooperating with the eye piece, the top being provided with a protractor so located as tobe rellected inthen'nirror about the center point, vthe protractor havingradial lines, certain of rwhicli .are` at` right angles `to each other andare Aso constructed as to 'define a cross, the'nfiirrorj beingprovided kwith inarksy located at idierent radial distances from the center `point ,of `the p mirror. v

4. An instrument for testing`lensesfcomprising .a top having `aii'eye piece,fand`a base'having a mirror provided with a center point cooperating with'the eye piece, the top being supplied with a protractor so located as to be reflectedfin' the lriiirrorabout the center point, 'the Aprotractor comprising an innercircle'and radial Alines extended outwardly from the circle,ycertainjof the radial lines which are'atzright angles to each other Vbeing accentuated to 'form a cross, theprotractor including other 'lines parallel to each other andparallel to'onex'of the cross-'forming lines, the 'mirror being 'supplied' with marks. located Yat different radial distances roin the `ce'I'iter'po-intbf the mirror.

In testimony that I claimthei'foregoing asiny own, Ihave hereto aiixed lmy signature in the presence oftwo witnesses.

HARRY Wiiafsoufo, D. Witnesses A.' S. UPPLEWHITE, 1M. iD., N. J. "Mmsrnxniuiss 

